1. Field of the Invention
The present disclosure relates to a radiation generating tube, a radiation generating unit provided with the radiation generating tube as a radiation source, and a radiation image taking system using the radiation generating unit.
2. Description of the Related Art
In the related art, a vacuum envelope including an insulating tube and a conductive electrode is used as a radiation generating tube used as a radiation source of a radiation generating unit. US Patent Application Publication No. 2007/0076849 A1 (U.S. Pat. No. 7,382,862) discusses a brazing material that is used for joining an insulating tube and an electrode of a radiation generating unit.
The vacuum envelope of the radiation generating tube requires sealing properties which maintain an internal vacuum atmosphere. Therefore, joining between the insulating tube and the electrode may be performed using a sufficient required amount of a conductive bonding material such as brazing material in order to enhance reliability by achieving a stable sealed state.
However, when the sufficient required amount of the conductive bonding material is used to join the insulating tube and the electrode, the conductive bonding material is easily protruding from between a bonded surface of the insulating tube and a bonded surface of the electrode facing each other (hereinafter, referred to as “between bonded surfaces” in this specification). When the conductive bonding material is protruding from between the bonded surfaces, an electric field tends to concentrate on a distal end of the protruding conductive bonding material when the radiation generating tube is driven, and hence, depending on the shape of the protruding conductive bonding material, there is a risk of induction of abnormal emission in the radiation generating apparatus in which the radiation generating tube is used.
In the radiation generating unit and the radiation image taking system, improvement of a voltage withstand property of the radiation generating tube to be used is required for accommodating size reduction or power increase of radiation to be emitted. In addition, operation stability increases and high voltage application is enabled with the improvement of the voltage withstand property, whereby improvement of performance is expected. As regards the vacuum envelope of the radiation generating tube, reliability and performance of the radiation generating unit and the radiation image taking system using the same may be improved by the improvement of the voltage withstand property simultaneously with a stable sealing property.